Recently, as an optical medium for recording music information or video information, an optical medium corresponding to regulations of a compact disc (CD), a digital versatile disc (DVD), and the like is being produced. Such an optical medium has a recording layer for recording information and recently an optical medium having the multi-layered recording layers to record large amount of information has been developed.
Conventionally in an optical medium having multi-layered recording layers, assuming that a side on which laser beam is irradiated is upper surface, when given information is recorded in a lower layer recording layer (hereinafter simply referred to as “lower layer”), transmissivity of the beam differs depending on the recording condition of the upper recording layer (hereinafter simply referred to as “upper layer), assuming that a side on which laser beam of the recording layer is irradiated is upper surface. Therefore, there is a case where power of the laser beam irradiated on the recording layer is changed and the given information cannot be appropriately recorded. Moreover, when given information recorded in a lower layer recording layer of an optical medium having multiple layers is reproduced, due to the same reason as the above, there is a case where information cannot be appropriately reproduced.
In such a case, to appropriately record or reproduce the given information to/from the recording layer, an information recording/reproducing device needs to carry out power control of laser beam on the basis of recording condition of the upper layer of the recording layer. Specifically, when recording in a lower layer of recording layers of an optical medium having multi-layered recording layers, the information recording/reproducing device irradiates optical beam to the optical medium and receives optical beam reflected by the optical medium as reflected light to control power of light beam for recording by reflection ratio of the reflected light (Patent Document 1).
Patent Document 1: Japanese Published Unexamined Patent Publication No. 2001-148133